Abstract of Research Plan: We have identified a rational approach to chemotherapy for African trypanosomiasis which depends upon the simultaneous inhibition of two parallel metabolic pathways which are essential for energy production by the parasites. First, there is an unusual mitochondrial electron transport system (the glycerophosphate oxidase system) associated with the primary glycolytic pathway. This can be blocked by salicylhydroxamic acid (SHAM). When the latter is blocked, the trypanosomes shift to another glycolytic pathway which produces glycerol. This alternate pathway can be blocked by exogenously supplied glycerol. Despite the specificity of these agents and the fact that combining SHAM and glycerol can cure experimental animals, the toxicity of SHAM at curative doses limits the practical utility of this drug combination. We propose to develop this approach into a useful chemotherapeutic regimen. Our preliminary studies have shown that several types of compounds can inhibit the glycolytic pathway susceptible to SHAM. Accordingly, we will pursue these leads via synthesis of analogues which contain functional groups believed to enhance activity. The compounds will be screened in vitro using two assay procedures. First, we will determine the ability of the compounds to inhibit the unique respiratory system of the parasites. Then we will incubate intact parasites with inhibitor + glycerol combinations and test their infectivity in fresh animals. When promising inhibitors have been identified, we will evaluate their acute toxicity, both alone and together with glycerol. Pharmacokinetic studies will then be conducted, both of the inhibitor alone and in combination with glycerol so as to determine an effective dose regimen in vivo. Finally, in vivo studies will be performed in infected animals. These in vivo studies will include, when appropriate, a mouse CNS model of the disease.